For the Hubbard model [1]} in lattices, formation of composite objects can be observed for both attractive and repulsive interactions [2]}. A doublon is such a composite object formed from two fermions. In Auger spectroscopy, certain lines and lineshapes in the spectra can be explained within the formalism of formation of bound pairs [3]}, [4]}, [5]}. In general, pairs formed from interacting particles show the properties different from constituent individual particles. For strongly interacting particles, their lifetimes are generally high [6]} and depend on interaction strengths. These strongly correlated pairs are now realized and observed in optical lattices within broad range of tuneable interaction strengths [7]}. Recently, the pairing phenomena have been also observed in optical lattices for spin excitations [8]} which are relevant for excited states near the ground ferromagnetic state. The bound states that arise in lattices from onsite and nearest neighbour interactions are also related to solitons [9]}, [10]}.
